Vehicle seats typically have a suspension used to support a person sitting in a seat while maximizing their comfort. As such, suspensions for vehicle seats are designed to provide comfort to a seat occupant while minimizing or absorbing and dampening bumps and jolts due to uneven, rough or rugged terrain encountered while riding in a vehicle. In fact, designing suspensions for vehicle seating sometimes requires a designer to consider a number of factors, such as, for example: seat vibration, natural frequency of the seat and suspension, the suspension characteristics of the vehicle, the type of terrain that will be encountered by the vehicle, how far the seat suspension is capable of travelling to absorb shocks during operation, vehicle seat size and packaging constraints, how the seat and suspension will behave during a crash, component and suspension cost, suspension reliability and durability, how easy and cost-effectively the suspension can be mass produced, as well as other design factors.
These design factors apply not only to vehicle seat suspensions for automotive vehicles, such as trucks and automobiles, but also to seat suspensions for off-road vehicle applications, such as garden tractors, lawn mowers, smaller all terrain vehicles, other preferably self-propelled lawn and garden equipment, and the like. In many cases, design considerations for these types of off-road vehicles can be equally complicated in part because of the severe manufacturing cost constraints imposed by manufacturers. In short, because these vehicles are relatively low cost, manufacturers demand vehicle seating which is also low cost but which must be reliable, durable, and which minimizes shocks, jolts, bumps and vibrations encountered during vehicle operation to prevent them from being directly transmitted to a person sitting in the seat.
Most, if not virtually all, of the seat suspensions for these types of vehicles are single pivot seat suspensions because of their simplicity, reliability and low cost. A single pivot seat suspension has a seat attached adjacent one end, typically its front end, to a base or frame by a single pivot. Spaced away from the pivot, typically adjacent the rear end of the seat, is at least one and typically a pair of springs disposed between the bottom of the seat and the seat base or frame. During operation, the seat hingedly swings about the seat attachment pivot in response to jolts, bumps, shocks and the like allowing the spring or springs to help absorb and dampen them.
In the past, most, if not virtually all, of these springs were metallic coil compression springs that were fixed in one position relative to the seat pivot. While coil spring suspensions are known which permit adjustment of the location of the spring or springs relative to the pivot, they require time consuming and expense-adding fasteners to fasten one end of the coil spring to the seat suspension frame in a manner which allows spring position adjustments to be made.
An example of such a seat suspension is disclosed in U.S. Pat. No. 4,198,092 to Federspiel which discloses a suspension for a lawn tractor seat that has a single coil spring which is secured at one end by a nut threadably received on a bolt that extends through an elongate adjustment slot in the seat frame and also through a hole in the end of the spring to clamp the end of the spring to the underside of the seat.
However, the other end of the spring, although preferably vinyl coated, can eventually scratch or mar the finish of that portion of a fender assembly of the lawn tractor which underlies and supports the spring. Moreover, the nut and bolt used to secure the spring to the seat require unnecessary, time consuming and costly manufacturing assembly steps to attach the spring to the seat during manufacturing the seat assembly. Additionally, coil springs are becoming less favored by seat suspension designers because they have a generally constant spring rate throughout their range compression. For example, when they bottom out during a particularly severe bump or jolt such that the spring is completely compressed, they bottom out particularly hard exposing the seat occupant to discomfort and possible injury. Sill further, coil springs often provide little damping ability therefore exposing a seat occupant to a rather bouncy ride which can ultimately undesirably translate into discomfort, nausea, and, quite possibly, at least some difficulty in steering or maneuvering the vehicle. Finally, coil springs have also become disfavored because they are noisy and, even if vinyl or plastic coated, the coating can wear away undesirably exposing the finish of the lawn tractor directly to the spring.
More recently, springs constructed of a urethane foam material have been substituted for metallic coil springs. While these types of seat suspensions employing foam springs have performed admirably out in the field, they have not heretofore been known to be adjustable for seat occupants of different weights and for the different types of terrain that can be encountered by the vehicle. This is likely because foam springs are difficult to attach to a seat base or a portion of a frame underlying the seat as a result of their flexible construction enabling them to be compressed inwardly in just about any direction, unlike coil springs.
Therefore, as a result of posing at least some difficulty in attaching foam springs to a seat or seat base underlying the spring, foam springs are attached to a vehicle seat or base underlying the seat in a manner which fixes their position relative to the front or rear of the seat and relative to the pivot of the seat, if the suspension is of single pivot construction. More specifically, it is known that foam springs have been attached using time consuming and expensive fasteners in a manner similar to that used for securing coil springs to a seat suspension. In another known method of securing a foam spring, an end of the spring is captured between a pair of fingers of the seat or seat base by sliding the spring between the fingers from the side, also fixing the position of the spring relative to the seat suspension pivot.
Vehicle seat adjusters are used to enable the fore and aft position of a vehicle seat to be adjusted relative to a steering wheel or vehicle dashboard permitting a seat occupant to optimize their comfort by increasing or decreasing legroom. While vehicle seat adjusters which use roller, ball or needle bearings disposed between a pair of interlocking metal seat slide rails are well known, they are relatively expensive to manufacture. In addition, the ball bearings and slide rails raise the seat off the vehicle floor limiting their use to vehicles which have more seating room. As a result, these types of conventional seat slide rails are not commonly used on the rather compact and inexpensive seats that are used in smaller, more inexpensive off-road vehicles, such as garden tractors and the like.
What is needed is a seat suspension for non-metallic, urethane, and other compression springs which permits the suspension to be adjusted to tailor the characteristics of the suspension for the weight of a seat occupant or the terrain likely to be encountered by the vehicle to give a seat occupant more comfort and protection against injury. What is further needed is a seat suspension for an elastomeric spring that allows one or both springs of the suspension to be moved relative to the front or rear of the seat to provide seat suspension weight adjustment capability. What is also needed is a foam spring single pivot seat suspension that permits one or both springs to be moved relative to the vehicle seat attachment pivot to provide seat occupant weight adjustment capability. What is still further needed is a seat suspension that is able to accommodate both foam springs and other non-metallic springs of generally cylindrical substantially elastomeric construction that can be shaped for the type and direction of load encountered. What is also needed is a seat suspension that is able to accommodate non-metallic springs of generally cylindrical and substantially solid construction while providing seat occupant weight and vehicle terrain compensating adjustment. What is still further needed is a vehicle seat adjuster for relatively small off-road vehicle applications that is relatively inexpensive to manufacture, durable, and which is of compact low profile construction.